Improvement in burglar-alarms



F. w. BL'AKEMURE.

BurgIar-'Alarms- Patented Dec. 23,1873.

INVENTORY.

UNITED STATES PATENT CDEEICE FRANCIS IV. BLAKEMORE, OF PHILADELPHIA,PENNSYLVANIA.

IMPROVEMENT IN BURGLAR-ALARMS.

Specification forming part of Letters Patent No. 145,836, dated December23, 1873; application iiled October 18, 1873.

To all whom fit may concern:

Be it known that I, FRANCIS W. BLAKEMORE, of Philadelphia, in the countyof Philadelphia and State of Pennsylvania, have invented. certain newand useful Improvements in Alarm Door-Bells; and I do hereby declare thefollowing to be a full, clear, and exact description of the invention,such as will enable others skilled vin the art to which it pertains tomake and use it, reference being had to the accompanying drawings, whichform part of this specification, in` which- Fignre 1 is a frontelevation of the alarmbell in position on the door. Fig. 2 is a view ofthe lower bracket, showing the crank-lever turned down to permit thedoor to be opened without giving an alarm.

My invention has for its object to provide an alarm door-bell of simpleconstruction, that may be manufactured at slight expense, and willoperate effectively, and without danger of easily getting out of order.The nature of my invention consists in the peculiar construction,arrangement, and combination of the devices for operating the clapper,which strikes by gravity, and is so arranged that it will be raised onlywhen the door is being opened, remaining undisturbed while the door isbeing closed. l

Referring to the accompanying drawing, A is the gong, screwed on ahorizontal central stai or standard, which is made fast, by suitablemeans, to a base-plate or bracket, B, de-

signed to be secured by screws to the top jam or frame of the door. C isthe clapper, connected, by the rod d, with drum D, which is journaled ona pin or pivot, b, on the baseplate B. b is another pin or fulerum onsaid base-plate, so arranged that as the rod d comes in contact with itas the clapper descends a spring or return mot-ion of said rod isproduced, elevating the clapper slightly, so as to permit the necessaryvibrations. E is an oblique flange or bevel on the drum D, and F is aplate or bracket, to be screwed on the door, having a pivotedcrank-lever, G, the weighted arm g of which is prevented from descendingbelow a horizontal line by the pin or stop g2.

The other arm g1 of the lever G projects above the upper line of thedoor, so as to impinge upon the flange E.

When the door is being started open the arm l g1 presses against theinner side of the flange, causing the-clapper C to rise. When the dooris opened still farther, the arm g1 passes the flange E, and the clapperdescends by gravity, and gives the alarm. In closing the door, the armg1 passes outside the flange without disturbing the latter, thecrank-lever G yielding, as shown in dotted linens.

The advantages of this construction are brieiiy as follows: The clapperbeing made to strike by gravity alone, the cost of manlifacture isgreatly reduced; and by dispensing with a spring for actuating saidclapper the most frequent cause of disarrangementl and breakage isavoided. So, too, by this construction it will be found impossible toopen the door without giving an alarm, as the bell will strike if thedoor be moved but an inch or two. lith other constructions the door maybe opened sufficiently, without giving an alarm, to permit a stick or apersons fingers tobe passed through the opening, and the clapper therebyprevented from striking.

1f desired, the crank-lever may be thrown out of engagement with theflange E, occupying the position shown in Fig. 2, when the door may beopened without giving an alarm.

IVhat I claim as my invention islhe drum D, provided with thegravity-hainmer C and oblique plate E, in combination with the plate B,secured to the door-j amb, and holding the gong A and stud b', and thebell-crank G, having the weighted arm g resting upon the stud gl, saidcrank being attached to the door, all constructed and arranged as shown,and for the purpose specified.

In testimony that I claim the foregoing I have hereunto set my hand this15th day of October, 1873.

FRANCIS W. BLAKEMORE.

Witnesses:

JAMES P. PETIT, EUGENE B. EAnsoN.

